Method of handling molten metal in a vacuum chamber



J1me 1967 A. SICKBERT ETAL 3,328,163

METHOD OF HANDLING MOLTEN METAL IN A VACUUM CHAMBER Filed March 21, 1963 4 Sheets-Sheet 1 Fly. 4

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I "S g r Hi .70 van for: Hoozr SICIFBERT 3 515659150 GER/r15 United States Patent 3,328,163 METHOD OF HANDLING MOLTEN METAL IN A VAtIUUM CHAMBER Adolf Sickbert, Wattenscheid-Eppendorf, and Siegfried Gerke, Bochum, Germany, assignors to Bochumer Verein fiir Gussstahlfabrikation Aktiengesellschaft, Bochurn, Germany, a corporation of Germany Filed Mar. 21, 1963, Ser. No. 266,982 Claims priority, application Germany, Mar. 22, 1962, B 66,457 2 Ciaims. (Cl. 75-49) This invention relates to the handling of molten metal and finds particular application in known procedures, wherein molten metal, for example, steel, is subjected to a vacuum for degasification or other effect.

In the vacuum treatment of metal, a ladle containing the molten metal can be positioned in a chamber which is vacuum tight and in which the molten metal is exposed to a vacuum. Alternatively, the molten metal contained in the ladle can be poured into a space enclosed by a suitable vessel, the space being maintained at a low pressure. The pouring into the vacuum can be performed so that the metal breaks into a spray upon exposure to the vacuum and, hence, a large surface area exposure is realized. This is in general a desired condition for the vacuum treatment. Where the molten metal is poured into a vacuum, it is common to utilize a funnel or small ladle for holding the metal to be introduced into the vacuum. The funnel is provided with an outlet in the bottom thereof and is mounted, vacuum tight, atop the vessel in which the vacuum is maintained. In a further refinement of the vacuum treatment of molten metal, tandem operation can be utilized wherein the molten metal is successively exposed to vacuums, usually the second or latter vacuum being at another pressure than the first or earlier vacuums.

In all of these treatments, it is desirable to utilize ladles having a refractory lining and provided with an outlet in the bottom thereof. A stopper in the form of an elongated element is disposed above the outlet and means are provided for selectively raising and lowering the stopper to, respectively, open and close the outlet for the flow of molten metal from the ladle. Means are provided for actuation of the stopper, and commonly the means comprises a lever for hand operation by the teemer and a mechanical linkage interconnecting the lever and the top of the stopper rod.

It is a principal object of the invention to provide improvement in respect to the stopper for molten metal handling ladles.

The invention provides apparatus for handling of the molten metal, and this apparatus includes a ladle having an outlet in the bottom thereof and a stopper of the type described above. The means for actuating the stopper comprises an electrical, linear drive means including an electric motor and a self-locking shaft operatively connected to said motor for axial movement thereof in response to the operation of the motor. The drive means is mounted on the outside of the ladle with the shaft extending vertically. Mechanical linkage means interconnect the shaft with the stopper so that movement of the stopper is effected in response to movement of the shaft. In a preferred embodiment of the invention, the electrical means utilized is a low voltage device. Desirably, the voltage is about 60 volts or less. The device of the invention is well suited to operation at low voltage, and the voltage can be selected so that it is appropriate to the conditions, particularly the vacuum conditions, to which the device will be subjected.

The invention is further described in the accompanying drawings wherein:

FIG. 1 is a schematic representation, in elevation and cross-section, of vacuum treatment apparatus according to Cir 3,328,l63 Patented June 27, 1967 the invention and wherein a tandem type operation is utilized, wherein the molten metal is successively exposed to two vacuums:

FIG. 2 is an enlarged view of a portion of a ladle as is shown in FIG. 1 and showing the mounting of an actuating means for the stopper;

FIG. 3 is a view corresponding with FIG. 2, but showing an alternative drive means;

FIG. 4 is a schematic representation of a tandem operation wherein metal can be subjected in series to different vacuum treatments; and

FIG. 5 is a showing, partially in cross-section, of an electrical, linear drive device as is utilized in the invention.

In the various views of the drawings, like reference characters refer to corresponding parts.

Referring to FIG. 1, a funnel 1 is mounted atop a ladle 2 which in turn is mounted atop vacuum vessel 3. Molten metal, for example steel, can be poured from a furnace into the funnel 1 and the funnel 1 releases the molten metal into the ladle 2. The ladle 2 is maintained under vacuum and upon the molten metal entering the vacuum space, it breaks into a spray and degasification results. From the ladle 2, the molten metal flows into vacuum chamber 3 which can be maintained at a lower vacuum than is the case for the vacuum in the ladle. Within the vacuum chamber 3, is a suitable ladle (not shown) for receiving the molten metal introduced into the vacuum chamber.

The funnel 1 has a refractory lining 4, an outlet 5a, a stopper 6 for the outlet, means for actuating the stopper, shortly to be described in detail, and a linkage interconnecting such means including the cross-arm 7 and the vertical connecting rod 8.

The ladle 2 is provided with a cover 9 which is mounted in vacuum sealed relation on the ladle 2. This cover is provided with a conduit opening 10 for communicating the inside of the ladle with a suitable vacuum drawing source. The ladle has a refractory lining 11 outlet opening 12, stopper l3, and the stopper 13 is connected with an actuating means, shortly to be described, by a linkage including the cross-arm 14 and the connecting rod 15. The cover 9 is formed to provide a sealed slideway 16 for the connecting rod 15 so that movement of the connecting rod to actuate the stopper can be elfected without significantly interferring with the vacuum maintained within the ladle.

The vacuum vessel 3 is provided with an inlet opening 17 for the molten metal and is provided with a conduit means 13 for connection to a suitable vacuum source.

According to the invention, the means for actuating the stopper comprises an electrical linear drive means. Such drive means are known in the art. They can comprise an electric motor directly connected to a threaded shaft for axial movement of the shaft in response to operation of the motor. The shaft can he threaded so that vertical movement thereof is elfected by a working on the threads by the motor or mechanical elements interconnecting the motor and threaded shaft. The threads should be of such a pitch that the shaft is self-locking by which is meant that slippage of the shaft will not occur when the shaft is in a fixed position. Thus, the threads are formed so that the cooperating engagement therewith provides suitable friction so that movement does not occur While the shaft is not being actuated by the motor and under the conditions of use applying. As shown in FIG. 2, the stopper actuating means includes the electrical, linear drive means 19 which is mounted on the outside of the vessel. Mounting plates 20 and 21 are suitably secured to the vessel, as by welding, and the linear drive means 19 is secured to the mounting plates by bolting 22. A power supply line 23 is connected to a suitable source of electric power (not shown). The shaft 5 is operatively interconnected with the motor of the linear drive means 19 and extends vertically upward therefrom. The shaft 5 is connected to the forked yoke 3a by the connector element 6, and the forked yoke 3a, in turn, is connected to the vertically extending connecting rod 24. This connecting rod corersponds with the connecting rods 8 and shown in FIG. 1. The connecting rod extends through guide blocks and 26 which are secured to the outside of the ladle by bolting 27. A lock 28 for manual operation, is provided for locking the connecting rod at a desired position when the electrical, linear drive means is not in use.

In the embodiment shown in FIG. 3, the electrical, linear drive means 19 is interconnected with the connecting rod 24 by a lever and fulcrum linkage. This linkage includes the lever arm 311 operatively mounted the pivot or fulcrum 31. The end portion 32 of the lever arm is provided with a slot 33 which receives pin 34, the pin 34 projecting from the connecting rod 24. The other end portion 35 of the lever 30 is provided with the slot 36, and this slot receives the pin 37 which is mounted on the shaft 5. Upon operation of the electrical, linear drive means to move the shaft 5 axially, the lever arm 30 is actuated and the pins 34 and 37 slide, respectively, in the slots 33 and 36.

In the embodiment shown in FIG. 4, there is shown an operation wherein, in a tandem operation, ladles are contained in vacuum chambers. Vacuum chamber 40 holds the ladle 41, and vacuum chamber 42 holds ladle 43. The vacuum chambers are provided with the conduit means 44 and 45 for communicating the same with a source of vacuum. A funnel 46 is mounted atop the upper vacuum chamber 40. The ladles 41 and 43 are provided, respectively, with stoppers 48 and 49, cross-arms 50 and 51, and connecting rods 52 and 53. An electrical, linear drive means (not shown in FIG. 4) is provided for each of the ladles 41 and 43 and is, in each case, connected with the ladle connecting rod by the forked arm 3a.

The embodiment shown in FIG. 4 indicates a particularly advantageous feature of the apparatus of the invention, especially where the electrical, linear drive means is for operation at a voltage of less than about volts. Thus, it will be observed that the ladles 41 and 43 are each within a vacuum chamber, and, accordingly, the electrical system of the electrical, linear drive means is exposed to a low pressure. At such pressure condition, electrical discharge is likely, and accordingly, the low voltage is particularly significant as it reduces the possibility of any glow discharge such as is apt to occur at high voltage and low pressure.

Low voltage operation according to the invention offers the further advantage of safety.

For the utilization of low voltage, the cross-section of the conductors of the electrical, linear drive must of course be appropriate, and it has been found that conductors sized for the desired voltage conditions are suitable for the service.

The providing of actuating means for the stopper, according to the invention, provides the further advantage that operation of the stopper can be controlled from a remote location, such as from a crane high above the actual vacuum treatment operation.

The utilization of a self-holding shaft for the electrical linear drive means, as by suitable thread form, provides the desired operating dependability in that the stopper can be securely held in a selected position. Further, such design of the shaft permits the making of fine adjustments by a smooth, shockfree operation, and provides the apparatus in a form having great strength. The strength of the actuating mechanism can be, and preferably is such that the stopper can be pressed into the outlet opening of its ladle to the extent that it actually deforms the refractory material surrounding the outlet opening. This not only permits the making of a tight seal but enables use of the stopper in the manner that irregularity of material at the outlet opening, as may be occasioned by usage and wear, can be removed by forcing the stopper into the outlet to the extent that it abrades the material and forms therein a smooth, uniform surface, which will facilitate the providing of a tight seal.

The fine adjutment of the stopper position which is obtainable with the apparatus of the invention is particularly significant in the vacuum treatment of metal, as it permits careful and accurate control of the rate of release of metal from a ladle into a vacuum space. Thus, the important vacuum treatment can be performed at the most suitable conditions.

In FIG. 5, there is shown an electrical linear drive according to the invention, a part of the outer housing of the drive being broken away to reveal internal structure thereof. This drive includes a housing 115, enclosure 118, guide head 117, and the cable connector box 119. Extending through the guide head 117 is the spindle 5. The spindle is coaxial with the housing and has a threaded portion 5b disposed remote from the guide head 117. The spindle threaded portion 5b is threaded into spindle nut 112. The spindle nut 112 is connected to an electric motor for rotation of the spindle nut by the motor. The motor includes the rotor 113 to which the spindle nut 112 is fixedly secured, and the stator winding 120. Upon operation of the motor, the spindle 5 is moved axially outwardly or inwardly by reason of the action of the spindle nut 112 on the spindle threaded portion 5b, The outwardly disposed portion of the spindle 5, which is disposed adjacent and extends through the guide head 117, is not threaded, and is provided with a keyway 130. A key 129 is fixedly secured to the guide head 117 and projects into the keyway 130. The cooperation of the key 129 and keyway 130 prevents rotation of the spindle and limits movement thereof to axial movement.

The mounting of the spindle nut 112 includes the stationary disc 123 secured in a fixed position by the nut 124. Bearing housing 126 is bolted to the stationary disc 123 and a rubber disc is interposed between the stationary disc and the bearing housing. A thrust bearing 127 is disposed in the bearing housing 126, and a rotating disc 121 is operatively connected with the thrust hearing. The rotating disc 121 is coupled to the spindle nut 112 by the coupling piece 122.

For the electrical linear drive shown in FIG. 5, the stator winding is a two-layer trickle winding, 48 grooves, 24 groups, 2 grooves per group, 60 wires per groove, 15 windings per course, 2 copper wires 1.1-1.2 mm. diameter in parallel, winding ditch 1:7, series mounting delta execution, 8 polar. The data for the squirrel cage are 2.2 kw., 26 a., 60 volt delta, 12 720' revolutions per minute.

While the invention has been described with respect to particular embodiments thereof, these embodiments are merely illustrative of the invention, and the invention is not limited thereto.

In detail, the invention is not restricted to the apparatus for a tandem operation as illustrated. The invention is of as great value in cases in which only one vacuum is applied to the metal, that means, that the lower vacuum chamber (3 in FIG. 1 or FIG. 2) is omitted. And very great value the invention has in all cases in which molten metal, especially steel, is tapped immediately from the melting furnace into the vacuum apparatus. The stopper of the funnel by means of which the metal flows from the furnace into the vacuum apparatus or vacuum ladle, can be operated only with great difliculty and danger in the conventional manner. The invention however exeludes all these dangers as the actuating of the stopper is now no longer to be done near the ladle and the tapping.

If a self-locking spindle is not used, a brake mechanism for the spindle must be provided for preferably a magnetic brake.

What is claimed is:

1. The method of handling molten metal which comprises providing the molten metal in a ladle having an outlet in the bottom thereof, and a stopper for said outlet comprising an elongated element disposed over said outlet with one end portion thereof disposed for selective insertion into and removal from the outlet to, respectively, seal and open the outlet, said ladle being outfitted with means for actuating said stopper, said means comprising an electrical, linear drive means including an electric motor and a self-holding shaft operatively connected to said motor for axial movement thereof in response to the operation of the motor, said drive means being mounted on the outside of the ladle with said shaft extending vertically, and said ladle being further outfitted with mechanical linkage means interconnecting said shaft with said stopper for moving the stopper for control of said outlet in response to movement of said shaft, providing said ladle and its associated electrical, linear drive means and mechanical linkage means in a vacuum chamber, providing vacuum within said chamber, and actuating said stopper by operation of the linear drive means to control flow of molten metal from the ladle.

2. Method according to claim 1 wherein said ladle is cooperating with the melting furnace during tapping.

References Cited UNITED STATES PATENTS OTHER REFERENCES German application 1,139,241, November 1962.

J. SPENCER OVERHOLSER, Primary Examiner.

MARCUS U. LYONS, MICHAEL V. BRINDISI,

Examiners. R. D. BALDWIN, Aassistant Examiner. 

1. THE METHOD OF HANDLING MOLTEN METAL WHICH COMPRISES PROVIDING THE MOLTEN METAL IN A LADLE HAVING AN OUTLET IN THE BOTTOM THEREOF, AND A STOPPER FOR SAID OUTLET COMPRISING AN ELONGATED ELEMENT DISPOSED OVER SAID OUTLET WITH ONE END PORTION THEREOF DISPOSED FOR SELECTIVE INSERTION INTO AND REMOVAL FROM THE OUTLET TO, RESPECTIVELY, SEAL AND OPEN THE OUTLET, SAID LADLE BEING OUTFITTED WITH MEANS FOR ACTUATING SAID STOPPER, SAID MEANS COMPRISING AN ELECTRICAL, LINEAR DRIVE MEANS INCLUDING AN ELECTRIC MOTOR AND A SELF-HOLDING SHAFT OPERATIVELY CONNECTED TO SAID MOTOR FOR AXIAL MOVEMENT THEREOF IN RESPONSE TO THE OPERATION OF THE MOTOR, SAID DRIVE MEANS BEING MOUNTED ON THE OUTSIDE OF THE LADLE WITH SAID SHAFT EXTENDING VERTICALLY, AND SAID LADLE BEING FURTHER OUTFITTED WITH MECHANICAL LINKAGE MEANS INTERCONNECTING WITH SHAFT WITH SAID STOPPER FOR MOVING THE STOPPER FORCONTROL OF SAID OUTLET IN RESPONSE TO MOVEMENT OF SAID SHAFT, PROVIDING SAID LADLE AND ITS ASSOCIATED ELECTRICAL, LINEAR DRIVE MEANS AND MECHANICAL LINKAGE MEANS IN A VACUUM CHAMBER, PROVIDING VACUUM WITHIN SAID CHAMBER, AND ACTUATING SAID STOPPER BY OPERATION OF THE LINEAR DRIVE MENAS TO CONTROL FLOW OF MOLTEN METAL FROM THE LADLE. 